Google's Chrome Web Store opened for business today, providing a centralized online marketplace for downloading Web apps for the Chrome operating system and the Chrome browser.

The marketplace, similar to Google's Android Market and Apple's iPhone App Store, is designed for Chrome 8, which was released last week. It offers apps, as well as extensions and themes, for customizing the browser.

Amazon said it is offering its Windowshop app, a stripped-down version of Amazon.com, on the marketplace. There also is an NPR news app, Facebook Photo Zoom, a New York Times app, and lots of games. The check-out process is integrated with Google Checkout.

The Chrome Web Store, which was expected to launch in October, was demonstrated at a Google event in San Francisco earlier today. The marketplace is only available in the U.S., but will expand to other countries early next year.

"The Chrome Web Store itself can be accessed using any browser. Currently only users of Google Chrome are able to install an app from the Chrome Web Store, which adds a shortcut on the Chrome browser's new tab page," a Google spokesperson said in a statement. "The protocols for describing and installing apps are all open-sourced and are free to be implemented by other browsers."

Updated 2:26 p.m. PTto correct that you do not need the Google Chrome operating system to use the store, 2:07 p.m. PTwith Google comment, and 1:10 p.m. PTwith more details.